During tests at five homes last fall, traces of thallium were detected in one of the drinking wells. Although below state or federal drinking water standards, authorities say more testing is needed to determine both the source and the severity of pollution they believe is leaching from coal ash pits nearly a quarter mile away.

The state has been concerned about the contamination since 2012, but says more study is needed to confirm whether Duke's nearby dumps are to blame.

In the meantime, Duke has been delivering bottled water to two homes with drinking wells that tests show contain chemicals associated with coal ash. Among them is thallium, once widely used in rat poison until it was banned in the 1970s because it is so toxic.

But environmentalists say state regulators have moved too slowly to protect the environment, ensure safe drinking water or hold Duke accountable.

"Any other polluter would have been held to a different standard than they held Duke to," said Carson Hartwell, the French Broad Riverkeeper. "If this was your local gas station down the street with groundwater contamination from a leaky oil tank, this would have been dealt with in a period of months, not in a period of years, with no real plan to deal with it."

More attention has been drawn to Duke and its coal ash pits, especially in North Carolina, after a massive Feb. 2 spill of coal ash at the company's plant on the Dan River. State lawmakers are currently considering legislation that would require the $50 billion company to move some or all of its toxic sludge from 33 unlined pits scattered at 14 sites across the state.

Towering above busy Interstate 26 and the French Broad River, the two ash dumps at Duke's Asheville plant cover 78 acres and hold an estimated 2.2 million tons of the gray muck.

A state hydrologist analyzing Duke's groundwater monitoring well data first raised concerns that chemicals from coal ash were threatening neighboring properties in early 2012, prompting the state Department of Environment and Natural Resources to launch an investigation, said Jay Zimmerman, a section chief at the state Division of Water Resources.

"We found something that we were a little concerned about," he told The Associated Press.

Since groundwater in North Carolina flows to rivers, Zimmerman said, the state began looking at the five homes between the ash pits and the French Broad that were using well water, taking samples three times between October 2012 and September 2013. Documents obtained by the AP through an open records request show the agency quickly focused on two homes built along the French Broad River, including the one with thallium.

State regulators are requiring Duke to prepare a site assessment plan to study the issue further, according to letters the agency sent in October to the owner of two homes and the Duke plant's manager.

Duke will use data collected from the off-site monitoring wells and other sources to determine if the ash dumps are the source of the contamination, Culbert said, adding that some substances could be naturally occurring.

State environment department spokeswoman Susan Massengale said evidence suggests a "physical connection" between the ash pits and wells at both homes, but there's not enough data to say for sure.

This is the latest development in a series of problems with Asheville's coal waste pits.

Regulators have known since 2010 that groundwater samples taken on the utility's property contained substances — some that can be toxic — in excess of state standards. They included readings for heavy metals contained in coal ash, including chromium and thallium.

In March, the state environmental agency found traces of thallium in three surface water samples collected near the ash pits, including one pulled directly from the "coal ash waste stream."

A year earlier, the state filed an enforcement action against Duke. Regulators warned that Duke's "continued operation of the Asheville plant in violation of groundwater standards" and without "assessing the problem and taking corrective action poses a serious danger to the health, safety and welfare of the people of the state of North Carolina and serious harm to the water resources of the state."

The detection of thallium in the groundwater was cited as a reason for concern. Some toxic metals occur naturally in the region, but the state said in documents that thallium on the plant property likely came from Duke's coal ash.

"Although thallium is a naturally occurring element, its presence in groundwater and specific occurrence at this site indicate impacts to groundwater resulting from coal burning activities," the document said.

More than a year later, the state has not yet ordered specific action from the utility to clean up the pollution.

Environmentalists say Asheville is indicative of the way state regulators have failed to enforce North Carolina laws protecting groundwater and communities from the dangers of ash pits.

The state should have forced Duke to take "immediate action" to eliminate the source of contamination years ago, said D.J. Gerken, a senior attorney for the Southern Environmental Law Center, which has filed lawsuits on behalf of citizens' groups to stop coal ash pollution. Instead, regulators allowed the Charlotte-based company to study the issue, something Gerken described as a delay tactic.

Massengale said regulators have taken steps to try to address the problems, including several legal actions.

"That has had some effect on the timelines associated with dealing with some of the coal ash issues," she said in an email.

In meetings with state regulators in Asheville, environmentalists warned years ago that pollution from the coal ash pits might be spreading toward homes near the French Broad River.

"We wanted them to take action," said Hartwell, who first began meeting with regulators in 2009. "We knew it was going to get worse."

Progress Energy, which owned the Asheville plant until it was acquired in a 2012 mega-merger with Duke, bought five acres in a housing development adjacent to the ash pits for $1.1 million in 2010 — a price tag far below what it would have cost to clean out the leaking coal ash pits,.

On the newly acquired land, the plant installed a groundwater monitoring well in 2012, replacing one at the edge of the plant that had been detecting substances exceeding state standards, including thallium, state documents show. Samples taken from the new monitoring well — about 200 feet downhill from the old one — exceeded state limits for some of the same elements, including thallium.

In an Oct. 17, 2013, letter to Kent Mottinger, who owns the two homes at the center of the state's sampling efforts, the department said thallium's presence in groundwater was "atypical."

A week later, G. Landon Davison, a regional supervisor for the state environment agency, wrote another letter to Mottinger with a warning about one of his wells that showed high concentrations of dissolved iron and manganese.

"The water should not be used for drinking and cooking unless an appropriate water treatment system is installed," Davidson wrote.

Davidson then sent a letter to Asheville Plant manager Garry Whisnant informing him that Duke had to "initiate site assessment activities" including the installation of monitoring wells. Under state orders, the company has been delivering bottled water to the house since October. Duke also "volunteered" to deliver water to the house next door — the one with the traces of thallium, Massengale said.

Mottinger rents both of the homes to tenants who include his ex-wife. Contacted by AP, he was reluctant to talk about the issue.

"I have faith that Duke and the state will do the right thing," he said. "I will be concerned if nothing is done about it."

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During tests at five homes last fall, traces of thallium were detected in one of the drinking wells. Although below state or federal drinking water standards, authorities say more testing is needed to determine both the source and the severity of pollution they believe is leaching from coal ash pits nearly a quarter mile away.

The state has been concerned about the contamination since 2012, but says more study is needed to confirm whether Duke's nearby dumps are to blame.

In the meantime, Duke has been delivering bottled water to two homes with drinking wells that tests show contain chemicals associated with coal ash. Among them is thallium, once widely used in rat poison until it was banned in the 1970s because it is so toxic.

But environmentalists say state regulators have moved too slowly to protect the environment, ensure safe drinking water or hold Duke accountable.

"Any other polluter would have been held to a different standard than they held Duke to," said Carson Hartwell, the French Broad Riverkeeper. "If this was your local gas station down the street with groundwater contamination from a leaky oil tank, this would have been dealt with in a period of months, not in a period of years, with no real plan to deal with it."

More attention has been drawn to Duke and its coal ash pits, especially in North Carolina, after a massive Feb. 2 spill of coal ash at the company's plant on the Dan River. State lawmakers are currently considering legislation that would require the $50 billion company to move some or all of its toxic sludge from 33 unlined pits scattered at 14 sites across the state.

Towering above busy Interstate 26 and the French Broad River, the two ash dumps at Duke's Asheville plant cover 78 acres and hold an estimated 2.2 million tons of the gray muck.

A state hydrologist analyzing Duke's groundwater monitoring well data first raised concerns that chemicals from coal ash were threatening neighboring properties in early 2012, prompting the state Department of Environment and Natural Resources to launch an investigation, said Jay Zimmerman, a section chief at the state Division of Water Resources.

"We found something that we were a little concerned about," he told The Associated Press.

Since groundwater in North Carolina flows to rivers, Zimmerman said, the state began looking at the five homes between the ash pits and the French Broad that were using well water, taking samples three times between October 2012 and September 2013. Documents obtained by the AP through an open records request show the agency quickly focused on two homes built along the French Broad River, including the one with thallium.

State regulators are requiring Duke to prepare a site assessment plan to study the issue further, according to letters the agency sent in October to the owner of two homes and the Duke plant's manager.

Duke will use data collected from the off-site monitoring wells and other sources to determine if the ash dumps are the source of the contamination, Culbert said, adding that some substances could be naturally occurring.

State environment department spokeswoman Susan Massengale said evidence suggests a "physical connection" between the ash pits and wells at both homes, but there's not enough data to say for sure.

This is the latest development in a series of problems with Asheville's coal waste pits.

Regulators have known since 2010 that groundwater samples taken on the utility's property contained substances — some that can be toxic — in excess of state standards. They included readings for heavy metals contained in coal ash, including chromium and thallium.

In March, the state environmental agency found traces of thallium in three surface water samples collected near the ash pits, including one pulled directly from the "coal ash waste stream."

A year earlier, the state filed an enforcement action against Duke. Regulators warned that Duke's "continued operation of the Asheville plant in violation of groundwater standards" and without "assessing the problem and taking corrective action poses a serious danger to the health, safety and welfare of the people of the state of North Carolina and serious harm to the water resources of the state."

The detection of thallium in the groundwater was cited as a reason for concern. Some toxic metals occur naturally in the region, but the state said in documents that thallium on the plant property likely came from Duke's coal ash.

"Although thallium is a naturally occurring element, its presence in groundwater and specific occurrence at this site indicate impacts to groundwater resulting from coal burning activities," the document said.

More than a year later, the state has not yet ordered specific action from the utility to clean up the pollution.

Environmentalists say Asheville is indicative of the way state regulators have failed to enforce North Carolina laws protecting groundwater and communities from the dangers of ash pits.

The state should have forced Duke to take "immediate action" to eliminate the source of contamination years ago, said D.J. Gerken, a senior attorney for the Southern Environmental Law Center, which has filed lawsuits on behalf of citizens' groups to stop coal ash pollution. Instead, regulators allowed the Charlotte-based company to study the issue, something Gerken described as a delay tactic.

Massengale said regulators have taken steps to try to address the problems, including several legal actions.

"That has had some effect on the timelines associated with dealing with some of the coal ash issues," she said in an email.

In meetings with state regulators in Asheville, environmentalists warned years ago that pollution from the coal ash pits might be spreading toward homes near the French Broad River.

"We wanted them to take action," said Hartwell, who first began meeting with regulators in 2009. "We knew it was going to get worse."

Progress Energy, which owned the Asheville plant until it was acquired in a 2012 mega-merger with Duke, bought five acres in a housing development adjacent to the ash pits for $1.1 million in 2010 — a price tag far below what it would have cost to clean out the leaking coal ash pits,.

On the newly acquired land, the plant installed a groundwater monitoring well in 2012, replacing one at the edge of the plant that had been detecting substances exceeding state standards, including thallium, state documents show. Samples taken from the new monitoring well — about 200 feet downhill from the old one — exceeded state limits for some of the same elements, including thallium.

In an Oct. 17, 2013, letter to Kent Mottinger, who owns the two homes at the center of the state's sampling efforts, the department said thallium's presence in groundwater was "atypical."

A week later, G. Landon Davison, a regional supervisor for the state environment agency, wrote another letter to Mottinger with a warning about one of his wells that showed high concentrations of dissolved iron and manganese.

"The water should not be used for drinking and cooking unless an appropriate water treatment system is installed," Davidson wrote.

Davidson then sent a letter to Asheville Plant manager Garry Whisnant informing him that Duke had to "initiate site assessment activities" including the installation of monitoring wells. Under state orders, the company has been delivering bottled water to the house since October. Duke also "volunteered" to deliver water to the house next door — the one with the traces of thallium, Massengale said.

Mottinger rents both of the homes to tenants who include his ex-wife. Contacted by AP, he was reluctant to talk about the issue.

"I have faith that Duke and the state will do the right thing," he said. "I will be concerned if nothing is done about it."